2,5,8,11-tetraboronic ester perylenediimides: A next generation building block for dye-stuff synthesis

Article abstract of DOI:10.1021/ol2008457

Via an unprecedentedly reported ruthenium catalyzed reaction, an efficient and straightforward method was developed for the synthesis of 2,5,8,11-tetraboronate perylenediimide derivatives. A possible reaction mechanism is proposed. The synthesis of 2,5,8,

Full text of DOI:10.1021/ol2008457

ORGANIC
LETTERS
2011
Vol. 13, No. 12
3012–3015
2,5,8,11-Tetraboronic Ester
Perylenediimides: A Next Generation
Building Block for Dye-Stuff Synthesis
€
Glauco Battagliarin, Chen Li,* Volker Enkelmann, and Klaus Mullen*
Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz,
Germany
lichen@mpip-mainz.mpg.de; muellen@mpip-mainz.mpg.de
Received April 1, 2011
ABSTRACT
Via an unprecedentedly reported ruthenium catalyzed reaction, an efficient and straightforward method was developed for the synthesis of
2,5,8,11-tetraboronate perylenediimide derivatives. A possible reaction mechanism is proposed. The synthesis of 2,5,8,11-tetra-iodo and tetra-
amino perylenediimides derivatives is also reported.
Perylenediimides (PDIs) are key chromophores in dye
stuff and pigment chemistry. Due to their thermal, chemi-
cal, and photochemical stability as well as their excellent
optical and electronic properties, they not only serve as
industrial colorants1 but also find applications in organic
field effect transistors,2 photovoltaic devices,3 and single
molecule spectroscopy.4
Since the first member of the family was discovered in
1913,5 PDIs have become one of the most important het-
erocyclic pigments. In 1959 their potential as highly fluores-
cent dyes was understood,6 but a more elaborate chem-
istry could be developed only during the 1980s, after the
discovery of two successful solubilizing strategies developed
by Langhals7 and BASF.8 The first one relies upon bulky
substituents at the imidic nitrogen with the possibility to
modulate solubility, with no geometrical modification of the
core and alteration of the optical and electronic properties.
The second implies the functionalization of the 1,6,7,12-
positions (bay-positions) via halogenation and successive
straightforward nucleophilic substitution9 or coupling reac-
tion.10 Solubility, optical, and electronic properties can be
finely tailored as desired. However, a geometric distortion of
the aromatic core is associated, dependent on the number
and nature of the substituents, with consequences on the
solid state properties such as self-assembling ability and
solid state fluorescence.11
€
(1) (a) Herrmann, A.; Mullen, K. Chem. Lett. 2006, 35, 978.
(b) Nagao, Y. Prog. Org. Coat. 1997, 31, 43.
(7) Langhals, H. Heterocycles 1995, 40, 477.
(2) (a) Jones, B. A.; Ahrens, M. J.; Yoon, M. H.; Facchetti, A.;
Marks, T. J.; Wasielewski, M. R. Angew. Chem., Int. Ed. 2004, 43, 6363.
(b) Schmidt, R. d.; Oh, J. H.; Sun, Y.-S.; Deppisch, M.; Krause, A.-M.;
(8) Seybold, G.; Wagenblast, G. Dyes Pigm. 1989, 11, 303.
€
(9) (a) Wurthner, F. Chem. Commun. 2004, 14, 1564. (b) Fan, L.; Xu,
€
Y.; Tian, H. Tetrahedron Lett. 2005, 46, 4443. (c) Wurthner, F.;
€
Radacki, K.; Braunschweig, H.; Konemann, M.; Erk, P.; Bao, Z.;
€
€
Stepanenko, V.; Chen, Z.; Saha-Moller, C. R.; Kocher, N.; Stalke, D.
Wurthner, F. J. Am. Chem. Soc. 2009, 131, 6215.
J. Org. Chem. 2004, 69, 7933.
€
(3) (a) Li, C.; Liu, M. Y.; Pschirer, N. G.; Baumgarten, M.; Mullen,
K. Chem. Rev. 2010, 110, 6817. (b) Zhan, X.; Tan, Z. a.; Domercq, B.;
An, Z.; Zhang, X.; Barlow, S.; Li, Y.; Zhu, D.; Kippelen, B.; Marder,
S. R. J. Am. Chem. Soc. 2007, 129, 7246.
€
(10) (a) Avlasevich, Y.; Li, C.; Mullen, K. J. Mater. Chem. 2010, 20,
3814. (b) Jiang, W.; Li, Y.; Yue, W.; Zhen, Y.; Qu, J.; Wang, Z. Org.
Lett. 2009, 12, 228. (c) Li, Y.; Tan, L.; Wang, Z.; Qian, H.; Shi, Y.; Hu,
W. Org. Lett. 2008, 10, 529.
€
(4) Weil, T.; Vosch, T.; Hofkens, J.; Peneva, K.; Mullen, K. Angew.
Chem., Int. Ed. 2010, 49, 9068.
(5) Kardos, M. Ber. Dtsch. Chem. Ges. 1913, 46, 2086.
(6) Geissler, G.; Remy, H.; (Hoechst AG), Ger. Pat. Appl., DE
1130099, 1959 (Chem. Abstr. 1962, 57, P11346f).
(11) (a) Su, W.; Zhang, Y.; Zhao, C.; Li, X.; Jiang, J. ChemPhysChem
€
2007, 8, 1857. (b) Wurthner, F. Pure Appl. Chem. 2006, 78, 2341. (c) Xu,
S.; Sun, J.; Ke, D.; Song, G.; Zhang, W.; Zhan, C. J. Colloid Interface
Sci. 2010, 349, 142. (d) Kaiser, T. E.; Wang, H.; Stepanenko, V.;
€
Wurthner, F. Angew. Chem. 2007, 119, 5637.
r
10.1021/ol2008457
Published on Web 05/24/2011
2011 American Chemical Society

substituents on the boron atom;16 (2) further limitations
arise from the ruthenium complex reactivity: in fact the
Murai catalyst (RuH2(CO)(PPh3)3) is involved in other
catalytic reactions, such as the conversion of nitroarenes
into tertiary amines,17 the rearrangement of oximes into
amides,18 transfer hydrogenation processes,19 and many
others;20 thus a consistent number of functional groups,
such as for example the already cited nitroarenes, internal
triple bonds, alcohols, and enones, must be avoided to
prevent side reactions; (3) even though the ortho-functio-
nalization of PDIs proves the possibility of choice to
address the 2,5,8,11-positions selectively, until now only
the formation of CꢀC bonds was demonstrated.
Figure 1. Perylenediimide.
To overcome these problems in our group we developed
a facile and straightforward synthesis of 2,5,8,11-tetra-
boronate PDIs, suitable building blocks for an extension
of the chemistry of the ortho-positions. The accessibility of
these sites is obtained, as in the previously reported
alkylation and arylation reactions of PDIs, using the
Murai catalyst. At the same time these systems were also
synthesized by the group of Shinokubo via an iridium
catalyzed borylation reaction.21
In 2009 a successful method for the selective functiona-
lization of the 2,5,8,11-positions of PDI (defined as ortho-
positions, Figure 1) was developed.12 Via ruthenium cata-
lyzed reactions between perylenediimides and terminal
alkenes or arylboronates it becomes possible to obtain
regioselectively tetraalkylated or tetraarylated PDIs; opti-
cal and electronic properties can be successfully tuned
without loss of the perylene core planarity. Enhanced
solubility and higher solid state fluorescence compared to
the unsubstituted parent compounds were demonstrated.13
Further, alkylation of the ortho positions suppresses inter-
molecular aggregation as well as the formation of inter-
molecular excited states between PDI molecules, yielding
an unprecedented photovoltaic power efficiency of poly-
thiophene:PDI blends.14
Nevertheless the synthetic method for the decoration of
the 2,5,8,11-positions still presents major disadvantages:
(1) the number of terminal alkenes and aryl boronates that
can be used in these reactions remains limited; olefins with
allylic hydrogens for example undergo rapid isomeriza-
tion and consequently give lower reaction yields15 whereas
the arylation procedure works in high yields with aryl
neopentylglycol boronates, but not as efficiently with other
A PDI and bis(pinacolato)diboron are mixed together
and dissolved in a mesitylene/pinacolone mixture. The
ruthenium catalyst is added to the reaction, and after
heating for 30 h at 140 °C the desired product is obtained
and isolated after chromatographic purification. This pro-
cedure is applied to PDIs 1a, 1b, and 1c. As already reported
in literature,12 the ruthenium catalyzed 2,5,8,11-functiona-
lization proceeds with higher yields in the presence of
sterically less demanding imide substituents, as in the case
of compounds a and b (60% and 70% yield, respectively,
Scheme 1). In the case of c, the desired tetraboronate is
formed in lower yields and cannot be isolated from the
mixture of mono-, bi-, and trisubstituted PDI.
Scheme 1. Ruthenium Catalyzed Borylation of PDIs
(12) (a) Nakazono, S.; Imazaki, Y.; Yoo, H.; Yang, J.; Sasamori, T.;
ꢀ
Tokitoh, N.; Cedric, T.; Kageyama, H.; Kim, D.; Shinokubo, H.; Osuka,
A. Chem.;Eur. J. 2009, 15, 7530. (b) Nakazono, S.; Easwaramoorthi, S.;
Kim, D.; Shinokubo, H.; Osuka, A. Org. Lett. 2009, 11, 5426.
(13) Bullock, J. E.; Vagnini, M. T.; Ramanan, C.; Co, D. T.; Wilson,
T. M.; Dicke, J. W.; Marks, T. J.; Wasielewski, M. R. J. Phys. Chem. B
2010, 114, 1794.
(14) Kamm, V.; Battagliarin, G.; Howard, I. A.; Pisula, W.; Mavrinskiy,
€
A.; Li, C.; Mullen, K.; Laquai, F. Adv. Energy Mater. 2011, 1, 137.
(15) Kakiuchi, F.; Chatani, N. Adv. Synth. Catal. 2003, 345, 1077.
(16) Kakiuchi, F.; Matsuura, Y.; Kan, S.; Chatani, N. J. Am. Chem.
Soc. 2005, 127, 5936.
(17) Feng, C.; Liu, Y.; Peng, S.; Shuai, Q.; Deng, G.; Li, C.-J. Org.
Lett. 2010, 12, 4888.
(18) Owston, N. A.; Parker, A. J.; Williams, J. M. J. Org. Lett. 2007,
9, 3599.
(19) Maytum, H. C.; Tavassoli, B.; Williams, J. M. J. Org. Lett. 2007,
9, 4387.
(20) (a) Anand, N.; Owston, N. A.; Parker, A. J.; Slatford, P. A.;
Williams, J. M. J. Tetrahedron Lett. 2007, 48, 7761. (b) Hall, M. I.;
Pridmore, S. J.; Williams, J. M. J. Adv. Synth. Catal. 2008, 350, 1975.
(c) Han, H.; Krische, M. J. Org. Lett. 2010, 12, 2844. (d) Pridmore, S. J.;
Slatford, P. A.; Daniel, A.; Whittlesey, M. K.; Williams, J. M. J.
Tetrahedron Lett. 2007, 48, 5115. (e) Shibahara, F.; Bower, J. F.;
Krische, M. J. J. Am. Chem. Soc. 2008, 130, 14120. (f) Slatford, P. A.;
Whittlesey, M. K.; Williams, J. M. J. Tetrahedron Lett. 2006, 47, 6787.
(g) Ueno, S.; Mizushima, E.; Chatani, N.; Kakiuchi, F. J. Am. Chem.
Soc. 2006, 128, 16516.
The proposed reaction mechanism is presented in
Scheme 2, and it is similar to the one reported by Kakiuchi
and Chatani for the ruthenium catalyzed arylation of aro-
matic ketones.16 Also in this case, to increase reaction yields,
pinacolone is used as a cosolvent to act as a scavenger of
(21) Teraoka, T.; Hiroto, S.; Shinokubo, H. Org. Lett. 2011, 13, 2532.
Org. Lett., Vol. 13, No. 12, 2011
3013

Scheme 2. Proposed Reaction Pathwaya
Scheme 3. 2,5,8,11-Tetraboronate-PDI as a Building Block
a Reaction starts with the coordination of the carbonyl by the
ruthenium(0) complex A to give intermediate B, followed by the forma-
tion of the ortho metalated intermediate C, after CꢀH bond cleavage.
Addition of the RuꢀH to the carbonyl group of pinacolone leads to the
production of the (alkoxy)-ruthenium intermediate D. Transmetalation
between the bis(pinacolato)diboron and the intermediate D results in the
formation of a trialkoxyborane and the aryl-boryl-ruthenium complex
E. Reductive elimination leading to CꢀB bond formation provides the
borylated product F and the regeneration of the active catalyst species A.
and sodium iodide in a THF/water mixture were used.22
The desired iodinated product could be obtained and
isolated. With compound 4 being a building block itself,
the nucleophilic replacement reaction using octylamine
was tested. Similarly to the amination reaction reported
in literature for naphthalene diimides,23 after heating the
tetraiodo derivative 4 at 130 °C under an argon atmo-
sphere, full conversion into compound 5 was observed.
the HꢀB species and avoid the undesired reduction of the
imide group. It is worth noting that, according to the
arylation protocol, the aryl boronate F should react with
another PDI molecule to form a PDI-dimer, but it has not
been observed. We believe the reason to be not sterical but
instead dependent on the nature of the boronate, deacti-
vated by the strongly electron-withdrawing aryl system and
consequently not available for the addition reaction.
To fully elucidate the structural features of 2,5,8,11-
tetraboronate PDIs, crystals of compound 2a were grown
from a chloroform/hexane mixture and characterized by
X-ray analysis (Supporting Informations, CCDC 823706).
As also reported by the group of Shinokubo,21 the core
maintains its planarity, while the sterically demanding
boronyl moieties strongly deviate from the plane of the
perylene unit.
To prove that the previously mentioned limitations in
the synthesis of ortho-tetrasubstituted PDIs can be over-
comed by using tetraboronate PDIs as intermediates
further reactions were performed.
The synthesis of derivative 3 was previously attempted
following the ruthenium catalyzed arylation method, but it
could not be obtained. Via Suzuki coupling of compound
2b with 4-bromobenzonitrile the desired tetrasubstitued
product could be easily synthesized (70% yield, Scheme 3),
isolated, and fully characterized.
Table 1. Optical and Electronic Properties of Reported PDIs
ε
λmax
λem
Ered1 LUMO HOMO
[V]e [eV]f [eV]g
PDIa [Mꢀ1cmꢀ1 b
]
[nm] [nm]c jfd
1a
2a
1b
2b
3
84 300
73 000
83 300
72 100
62 900
72 300
54 200
526 538
538 548
526 538
538 548
528 542
0.99 ꢀ0.95 ꢀ3.85 ꢀ6.13
0.89 ꢀ0.96 ꢀ3.84 ꢀ6.07
0.97 ꢀ0.95 ꢀ3.85 ꢀ6.13
0.83 ꢀ0.97 ꢀ3.83 ꢀ6.06
0.69 ꢀ0.90 ꢀ3.90 ꢀ6.16
4
518
ꢀ
ꢀ
ꢀ0.89 ꢀ3.91 ꢀ6.21
5
512 608
0.05 ꢀ1.59 ꢀ3.21 ꢀ5.61h
a Optical properties measured in toluene for compounds 1a, 1b, 2a,
and 2b, in dichloromethane for compounds 3, 4, and 5. b Measured at
λmax. .
c Excited at λmax d Determined using Rhodamine 6G in ethanol as
standard. e Half-wave potentials, determined by cyclic voltammetric
measurement in 0.1 M solution of Bu4NPF6 in CH2Cl2: vs Fc/Fcþ.
f Estimated vs vacuum level from ELUMO = ꢀ4.80 eV ꢀ Ered1
from the optical absorption/emission data. h Estimated vs vacuum level
.
g Esti-
mated from HOMO = LUMO ꢀ Eg, where Eg = optical gap, calculated
from ELUMO = ꢀ4.80 eV þ Eox1
.
All the compounds 2, 3, 4, and 5, as well as their
precursors 1a and 1b, were characterized by cyclic voltam-
metry, UVꢀvisible optical absorption spectroscopy, and
Additionally, the replacement of the boronate groups
into iodine atoms was explored. To do so, chloramine-T
(22) Kabalka, G. W.; Akula, M. R.; Zhang J. Nucl. Med. Biol. 2002,
29, 841.
€
€
(23) Roger, C.; Wurthner, F. J. Org. Chem. 2007, 72, 8070.
3014
Org. Lett., Vol. 13, No. 12, 2011

while for compound 4 only a lowering of less than 0.1 eV
occurs.
To conclude we have developed an efficient and
straightforward method for the synthesis of 2,5,8,11-
tetraboronate PDIs. The potential of these derivatives
for the further development of the chemistry of the
ortho-positions was successfully demonstrated. Addi-
tionally replacement of the boronate groups with iodine
atoms could be achieved, demonstrating for the first
time the possibility to selectively introduce halogen
atoms in the 2,5,8,11-positions.
We expect that, due to the broad chemistry of boronic
esters, tetraboronate perylendiimides represent the next
generation of building blocks for the development of a
complete chemistry of the ortho-positions of PDIs and
the obtainment of new advanced functional materials.
Additionally the possibility to selectively form CꢀB
bonds in the ortho-position of carboxylic derivatives
via ruthenium catalyzed reaction was demonstrated.
Studies to fully understand the mechanism of the bor-
ylation reaction and its applications are still ongoing in
our laboratories.
Figure 2. Normalized UVꢀvisible absorption spectra of com-
pounds 4 (black) and 5 (violet) and fluorescence spectra (red) of
compound 5 in dichloromethane (λexc = 512 nm).
photoluminescence spectroscopy (Table 1). It is possible to
note that the introduction of four alkylamine moieties in the
2,5,8,11-positions of the perylene core broadens the absorp-
tion (Figure 2) but does not cause a strong color change as in
the case of tetra-amino-substituted naphthalenediimides.23
Additionallythe introduction of four iodine atoms causes
a complete quenching of the fluorescence, due to the heavy
atom effect.
As expected, the information obtained by electrochemi-
cal investigation shows that the introduction of alkylamine
moieties and iodine atoms in the ortho-positions of the
perylene core causes opposite effects on the HOMO and
LUMO energies; in the first case, a consistent lifting is
observed(0.64eVfortheLUMO and 0.52fortheHOMO),
Acknowledgment. We gratefully acknowledge the fi-
nancial support from the DFG Priority Program SPP1-
355, the One-P large-scale project no.212311, and BASF
SE. G.B. thanks the IMPRS Ph.D. program for the
economical support.
Supporting Information Available. Full experimental
details and characterization data. CIF file for the X-ray
analysis of 2a. This material is available free of charge via
the Internet at http://pubs.acs.org.
Org. Lett., Vol. 13, No. 12, 2011
3015